Heat exchanger, method of manufacturing heat exchanger and plate-shaped fin for heat exchanger

ABSTRACT

A heat exchanger comprises: a plurality of plate-shaped fins, which are laminated on each other at predetermined intervals, on which a plurality of insertion holes having burring portions are formed; and a plurality of tubes inserted into the insertion holes, wherein the burring portions and the tubes are brazed to each other, and at least the burring portions of the plate-shaped fins are composed of a plurality of metallic layers for displacing the burring portions to the side of the insertion holes according to a rise in temperature at the time of brazing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat exchanger, in which a plurality of tubes are inserted into a plurality of laminated plate-shaped fins, and to a method of manufacturing the heat exchanger. The present invention also relates to a plate-shaped fin used for the heat exchanger.

2. Description of the Related Art

As disclosed in the official gazette of JP-A-10-62084, a conventional heat exchanger is known in which tubes (These tubes are referred to as flat heat exchange tubes in this Patent Document.) are inserted into insertion holes formed in a plurality of plate-shaped fins which are laminated. In this heat exchanger, rising pieces are formed on two sides, which are opposed to each other, of the opening edge of the insertion hole. One rising piece is bent from the rising point toward the other rising piece side, and the forward end of one rising piece is located outside the rising point.

The forward end of the rising piece, which is bent in this way, is pushed in the inserting direction of the tube. Under the condition that the bent portion is deformed outwardly, the tube is inserted into the insertion hole. After that, when the pushing force is released, the rising piece and the tube are tightly contacted with each other.

Further, the plate-shaped fin and the tube are brazed to each other by the brazing material provided on at least one of the surfaces of the plate-shaped fin and the tube.

Due to the above structure, the plate-shaped fin and the tube can be tightly contacted with each other and the assembling work can be made easy.

However, the above conventional heat exchanger is disadvantageous as follows. In order to deform the rising piece at the time of assembling, it is necessary to apply and release a pushing force, which increases the number of man-hours needed for the assembling work. Further, in the above Patent Document, no specific descriptions are made into the method of applying the pushing force. Therefore, it is difficult to put the above heat exchanger into actual use.

SUMMARY OF THE INVENTION

The present invention has been accomplished to solve the above conventional problems. An object of the present invention is to provide a heat exchanger characterized in that: a tube can be excellently inserted into an insertion hole without increasing the number of man-hours needed for the assembling work; and the plate-shaped fin and the tube are tightly contacted with each other. Another object of the present invention is to provide a method of manufacturing the heat exchanger. Still another object of the present invention is to provide a plate-shaped fin used for the heat exchanger.

In order to accomplish the above object, the present invention adopts the following technical means.

In order to accomplish the above object, according to a first aspect of the present invention, there is provided a heat exchanger comprising: a plurality of plate-shaped fins (110), which are laminated at predetermined intervals, on which a plurality of insertion holes (111) having burring portions (112) are formed; and a plurality of tubes (120) inserted into the insertion holes (111), wherein the burring portions (112) and the tubes (120) are brazed to each other, and at least the burring portions (112) of the plate-shaped fins (110) are composed of a plurality of metallic layers for displacing the burring portions (112) to the side of the insertion holes (111) according to a rise in the temperature at the time of brazing.

Due to the foregoing, at a temperature at which the tube (120) is inserted into the insertion hole (111), a gap is formed between the tube (120) and the burring portion (112). Alternatively, when both are contacted with each other, the tube (120) can be smoothly inserted into the insertion hole (111). At the time of brazing, the burring portion (112) can be positively contacted with or tightly contacted with the tube (120) side. Therefore, brazing can be surely conducted. In this way, the tube (120) can be smoothly inserted into the insertion hole (111) and brazed to the burring portion (112) without an increase in the number of man-hours which is necessary for applying and releasing a pushing force as described in the prior art.

According to a second aspect of the present invention, the metallic layer can be composed of a core material (110A) and a brazing material (110B) clad onto one of the faces of the core material (110A).

As in the third aspect of the present invention, when the sacrificial corrosion material (110 c), which conducts a sacrificial corrosion action upon the tube (120), is provided on a face on the side opposite to the face on which the brazing material (110B) is provided, it is possible to suppress the occurrence of corrosion on the tube (120) side. Therefore, it is possible to prevent a leakage of the inner fluid from the tube (120) and the life of the heat exchanger can be prolonged.

According to a fourth aspect of the present invention, the metallic layer may include: a core material (110A); a first brazing material (110B); and a second clad material (110D), wherein and the first brazing material (110B) and the second clad material (110D) are respectively clad on a surface and a reverse face of the core material (110A).

Due to the foregoing, the brazing material (110D) can be supplied from a portion closer to a portion where the tube (120) and the burring portion (112) are joined to each other at the time of brazing. Therefore, the brazing property can be further enhanced.

According to a fifth aspect of the present invention, a direction, in which rising points of the burring portions (112) are connected to each other is the same as a rolling direction of the plate-shapes fins (110).

Due to the foregoing, the direction in which the rising points of the burring portions (112) are connected to each other, becomes the same as the direction of the metallic crystal grains of the fin which is determined by rolling. Therefore, rigidity of the burring portion (112) in the displacement direction can be lowered and the burring portion (112) can be more smoothly displaced.

According to a sixth aspect of the present invention, a cross section of the tube (120) is formed into a flat shape, the burring portions (112) are formed on two sides of the insertion hole (111) corresponding to a long side of the flat cross section of the tube (120), and a positioning portion (113) for positioning the tube (120) is provided in a portion of the insertion hole (111) corresponding to an end portion of the flat cross section in the longitudinal direction.

Due to the foregoing, when the positioning portion (113) is arranged on the center line of the insertion hole (111), a distance between the burring portions (112) on two sides and the tube (120) can be made uniform. Therefore, both of the burring portions (112) on the two sides can be positively contacted with the tube (120).

According to a seventh aspect of the present invention, two cutout portions (114), which are cut out onto the side opposite to the insertion hole side, are formed at a peripheral edge of the insertion hole (111), and the burring portion (112) is formed at a base point of a connecting line (112 a) to connect bottom portions of the cutout portions (114) between the two cutout portions (114).

Due to the foregoing, the substantial length of the burring portion (112) can be elongated, and the burring portion (112) can be more positively contacted or closely contacted with the tube (120).

According to an eighth aspect of the present invention, a rib (115), which is extended along a side portion of the plate-shaped fin (110), is provided in the side portion of the plate-shaped fin (110) in a direction in which a plurality of tubes (120) are arranged.

Due to the foregoing, even when the overall plate-shaped fin (110) is composed of a plurality of metallic layers, a displacement of the general portions except for the burring portion (112) can be positively suppressed or a displacement of the overall fin (110) can be positively suppressed at the time of brazing.

According to a ninth aspect of the present invention, the burring portions (112) are arranged at the peripheral edge of the insertion hole (111) being opposed to each other, and a portion, the rising height of which is higher than the opposing side, is formed in each burring portion (112).

Due to the foregoing, in a portion where the height of rising of the burring portion (112) is large, it is possible to obtain a large displacement of the burring portion (112). Therefore, the burring portion (112) can be positively contacted or closely contacted with the tube (120). Under the condition that at least this portion is made to be a starting point, the brazing material (110B) gets into the gap portion (130) formed between the tube (120) and the burring portion (112) by the capillary phenomenon. Therefore, brazing can be positively executed.

According to a tenth aspect of the present invention, a thickness removing portion (116) is formed in the neighborhood of a portion where the rising points of the burring portions (112) are connected to each other or in the neighborhood of the base point.

Due to the foregoing, the rigidity can be lowered at the rising point of the burring portion (112) or the base point. Therefore, even in the positional relation in which the burring portion (112) is contacted with the tube (120) at the time of inserting the tube (120), the burring portion (120) can be easily deformed and the resistance can be reduced at the time of inserting the tube (120).

According to an eleventh aspect of the present invention, the burring portion (112) includes: a first metallic layer (110A) arranged on the insertion hole (111) side; and a second metallic layer (110B), which is arranged on the side opposite to the insertion hole side, to be penetrated into the first metallic layer (110A) and to swell the first metallic layer (110A) so that the burring portion (112) can be displaced to the insertion hole (111) side.

Due to the foregoing, at the time of brazing, the burring portion (112) can be positively contacted or closely contacted with the tube (120) side.

According to a twelfth aspect of the present invention, the burring portion (112) may include a plurality of metallic layers (110A1, 110A2), the coefficients of thermal expansion of which are different from each other so as to exhibit the bimetal effect so that the burring portion (112) can be displaced to the insertion hole (111) side.

According to an thirteenth aspect of the present invention, there is provided a method of manufacturing a heat exchanger comprising the steps of: laminating a plurality of plate-shaped fins (110), in which a plurality of insertion holes (111) having the burring portions (112) are formed, at regular intervals; inserting a plurality of tubes (120) into the insertion holes (111); and brazing the burring portions (112) and the tubes (120) to each other, wherein at least the burring portions (112) of the plate-shaped fins (110) are composed of a plurality of metallic material layers so that the burring portions (112) can be displaced to the insertion holes (111) side according to a rise in the temperature to the brazing temperature, and after the tubes (120) have been inserted into the insertion holes (111), the burring portions (112) are displaced and contacted with the tubes (120) and brazing is conducted.

Thereby, the above-identified method can be a method of manufacturing the first aspect of a heat exchanger (100).

According to a fourteenth aspect of the present invention, gaps are formed between the burring portions (112) and the tubes (120) when the tubes (120) are inserted into the insertion holes (111).

Due to the foregoing, when the tube (120) is inserted into the insertion hole (111), the working property can be enhanced.

According to a fifteenth aspect of the present invention, the tubes (120) are inserted into the insertion holes (111) at the normal temperature.

Due to the foregoing, it becomes unnecessary to conduct a special temperature setting, and the tube (120) can be easily inserted.

According to a sixteenth aspect of the present invention, the burring portion (112) includes: a first metallic layer (110A) arranged on the insertion hole (111) side; and a second metallic layer (110B), which is arranged on the side opposite to the insertion hole side, to be penetrated into the first metallic layer (110A) and to swell the first metallic layer (110A) so that the burring portion (112) can be displaced to the insertion hole (111) side.

Thereby, the above-identified method can be a method of manufacturing the eleventh aspect of a heat exchanger (100).

According to a seventeenth aspect of the present invention, the burring portion (112) including: a plurality of metallic layers (110A1, 110A2), the coefficients of thermal expansion of which are different from each other so as to exhibit the bimetal effect so that the burring portion (112) can be displaced to the insertion hole (111) side.

Thereby, the above-identified method can be a method of manufacturing the twelfth aspect of a heat exchanger (100).

The eighteenth to twenty-ninth aspects of the inventions relate to a plate-shaped fin used for a heat exchanger in which the burring portions (112) are provided in the insertion holes (111) into which a plurality of tubes (120) are inserted, while the above-identified fins are provided in the first to twelfth aspect of heat exchangers to have substantially the same technical effect.

Incidentally, the reference numerals in parentheses, to denote the above means, are intended to show the relationship of the specific means which will be described later in an embodiment of the invention.

The present invention may be more fully understood from the description of preferred embodiments of the invention set forth below, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is an exploded perspective view showing a heat exchanger of the first embodiment;

FIG. 2 is a front view showing a tube of the first embodiment;

FIG. 3A is a front view showing a plate fin of the first embodiment;

FIG. 3B is a sectional view taken on line A-A in FIG. 3A;

FIG. 4 is an enlarged sectional view showing a burring portion of FIG. 3A;

FIG. 5 is a block diagram showing an outline of the process of manufacturing the heat exchanger of the first embodiment;

FIG. 6 is a sectional view showing a state of brazing between the plate fin and the tube of the first embodiment;

FIG. 7 is an enlarged sectional view showing a burring portion of Variation 1 of the first embodiment;

FIG. 8 is an enlarged sectional view showing a burring portion of Variation 2 of the first embodiment;

FIG. 9 is a perspective view showing a plate fin of the second embodiment;

FIG. 10A is a front view showing a plate fin of the third embodiment;

FIG. 10B is a perspective view showing the plate fin of the third embodiment;

FIG. 11 is a perspective view showing a plate fin of the fourth embodiment;

FIG. 12 is an enlarged sectional view showing a burring portion of Another Embodiment 1;

FIG. 13A is a front view showing a plate fin of Another Embodiment 2;

FIG. 13B is a sectional view taken on line B-B in FIG. 13A;

FIG. 14A is a front view showing a plate fin of Another Embodiment 3; and

FIG. 14B is a sectional view taken on line C-C in FIG. 14A.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First of all, referring to FIGS. 1 to 6, the first embodiment of the present invention will be explained below. FIG. 1 is a perspective view showing a heat exchanger 100 of the first embodiment, FIG. 2 is a front view showing a tube 120, FIG. 3A is a front view showing a plate fin 110, FIG. 3B is a sectional view taken on line A-A in FIG. 3A, FIG. 4 is an enlarged sectional view showing a burring portion 112 of FIG. 3A, FIG. 5 is a block diagram showing an outline of the process of manufacturing the heat exchanger 100, and FIG. 6 is a sectional view showing a state of brazing between the plate fin 110 and the tube 120.

The heat exchanger 100 of this embodiment is arranged in a heat pump cycle of a hot-water supplying unit for domestic use and applied to an air heat exchanger (evaporator) for absorbing heat from the outside air. The heat exchanger 100 is composed as follows. As shown in FIGS. 1 and 2, a plurality of tubes 120 are inserted (or penetrate) into the insertion holes 111 of a plurality of plate fins (which correspond to the plate-shaped fins of the present invention) which are laminated at predetermined intervals, so that the core portions 101, which become the heat exchange portion, can be composed. Both end portions of the tubes 120 in the longitudinal direction are connected to the tube holes 143 of a pair of header tanks 141, 142.

In this connection, each tube 120 has a plurality of circular passages 121 inside. A cross section of each tube 120 is formed into a flat shape (for example, the thickness d is 1 mm and the size in the longitudinal direction is 23 mm) by means of extrusion. Each header tank 141, 142 is composed in such a manner that the caps 144 are provided at both end portions in the longitudinal direction of a cylindrical member which is formed, for example, by means of extrusion. The refrigerant inlet portion 151 and the refrigerant outlet portion 152, which are respectively communicated with the inside, are provided in the header tanks 141, 142.

The above components are made of aluminum or an aluminum alloy. After the above components are assembled into the shape of the heat exchanger 100, they are integrally brazed with each other by the brazing material previously provided on surfaces of predetermined components (In this case, the predetermined components are the plate-shaped fin 110 and the header tanks 141, 142.)

The refrigerant flows in the heat pump cycle from the refrigerant inlet portion 151 into the header tank 141 and is distributed into the tubes 120. After that, the refrigerant is collected into the header tank 142 and flows out from the refrigerant outlet portion 152. When the refrigerant is circulated in the tubes 120 (the core portion 101), heat is exchanged between the refrigerant and the outside air, so that heat is absorbed from the outside air by the refrigerant.

In the heat exchanger 100 of the present embodiment, the joining structure of joining the plate-shaped fin 110 to the tube 120 is characterized, and the detail will be explained below by referring to FIGS. 3A to 4.

The plate-shaped fin 110 (which will be referred to as a fin hereinafter) is a thin strip member. In the fin 110, a plurality of insertion holes 111 are provided in the longitudinal direction (shown in FIG. 1). Each insertion hole 111 provided in the plate-shaped fin 110 is formed into a flat shape so that it can correspond to the cross sectional shape of the tube 120 (shown in FIG. 2). On the two sides of the insertion hole 111 corresponding to the long side, the burring portions 112, which are opposed to each other, are formed by means of press forming. On the end portion sides of the insertion hole 111 in the longitudinal direction, the positioning portions 113, the shapes of which are respectively formed into a crescent shape, are formed being opposed to each other simultaneously with the formation of the burring portion 112 by means of press forming. The positioning portions 113 are arranged at the central position of both the burring portions 112. The inside size of the positioning portions 113 is determined so that the positioning portions 113 can be substantially contacted with the end portions in the longitudinal direction of the flat cross section of the tube 120.

In this case, in portions respectively adjacent to the positioning portions 113 (on the central side of the insertion hole 111), the cutout portions 114, which are cut out so that the cutout portions can extend to the side opposite to the insertion hole side. In this case, two cutout portions 114 are formed for one long side, that is, four cutout portions 114 are formed in total. Each burring portion 112 described above is provided between two cutout portions 114. The burring portion 112 is formed into a gentle R-shape so that the rising height of the edge portion of the burring portion 112 can be “h” from the base point which is the connecting line 112 a of the cutout portions 114. In this case, the connecting line 112 a corresponds to the line connecting the rising points of the burring portions 112. In this connection, the direction of the connecting line 112 a is the same as the rolling direction (shown by arrows in FIGS. 3A and 3B) of the fin 110 composed of a strip material.

The size D of the burring portion 112 on the opening side (the forward end side) is set to be larger than the thickness d of the tube 120. Therefore, when the tube 120 is inserted into the insertion hole 111 in the assembling stage, that is, when the tube 120 is inserted in the direction of the white arrow in FIG. 4, the gap portion 130 ((D−d)/2) can be formed between the wall face of the tube 120 and the burring portion 112.

In the present embodiment, the edge rising height h=1.18 mm, R=1.98 mm and the opening side size D=1.2 mm, and the size L between the connecting lines 112 a, which are the base points of the burring portions 112 opposed to each other, is 4.97 mm.

The fin 110 is composed of a core material 110A, which corresponds to the first metallic layer of the present invention, and a brazing material, which corresponds to a brazing material of the present invention, that is, which corresponds to the second metallic layer of the present invention, previously clad on one face of the core material 110A. The brazing material 110B is provided on a face of the burring portion 112 on the opposite side to the insertion hole side. In this case, the material of the core material 110A is an alloy, the alloy number of which is 3003 (JIS-H-4000), and the thickness is 0.08 mm. The material of the brazing material 110B is an alloy, the alloy number of which is 4045 (JIS-Z-3263), and the thickness is 0.02 mm. The silicon (Si) content of the brazing material 110B is higher than that of the core material 110A. Therefore, the coefficient of thermal expansion of the brazing material 110B is different from that of the core material 110A. The coefficient of thermal expansion of the brazing material 110B is lower than that of the core material 110A.

In this embodiment, when the temperature of the brazing material 110B is raised to a temperature close to the melting temperature, metal contained in the composition of the brazing material 110B penetrates or diffuses in the core material 110A. Therefore, the core material 110A is swelled. As a result, a side of the core material close to the brazing material 110B is greatly swelled. Accordingly, the entire core material 110A is warped being deformed to the side on which the brazing material 110B is not provided. That is, when the temperature of the fin 110 is raised from the normal temperature to the brazing temperature, an irreversible deformation is caused in the fin 110. Concerning the burring portion 112, when the fin material 110 is partially raised in the direction opposite to the direction of the irreversible deformation and mechanically given a plastic deformation, the burring portion 112 can be formed. Therefore, the irreversible deformation caused by the temperature change deforms the burring 112 in the direction of restoring the above mechanical plastic deformation. That is, the burring portion 112 is composed of the two metallic layers (the core material 110A and the brazing material 110B) so that the burring portion 112 can laminated by the two metallic layers.

Therefore, as shown by the arrows in FIGS. 3A and 3B, the burring portion 112 is displaced to the insertion hole 111 side by a rise in the temperature to the brazing temperature at the time of brazing described later, that is, the opening side size D is reduced to the size E. In the present embodiment, when the shape of the burring portion 112 is set as described above and when the material of each portion is set as described above, at the temperature (600° C. as described later) of brazing, the opening side size E is reduced to be smaller than the thickness d of the tube 120 (the opening portion size E=0.8 mm).

Next, by referring to FIG. 5, the method of manufacturing the above heat exchanger 100 will be briefly explained as follows. First of all, the fin 110 explained above is formed by means of press forming. The tube 120 is formed by means of extrusion. These fin 110 and tube 120 are respectively prepared separately from each other as described above. The header tanks 141, 142 are formed by means of extrusion. The tube hole 143 is formed on the side wall of each header tank. Then, the cap 144, the refrigerant inlet portion 151 and the refrigerant outlet portion 152 are respectively attached and temporarily caulked to each header tank 141, 142.

After that, a predetermined number of fins 110 are laminated. While the positioning portions 113 are being used as guides, each tube 120 is inserted (penetrated) into each insertion hole 111, so that the core portion 101 can be assembled. Then, both end portions in the longitudinal direction of each tube 120 are engaged with the tube holes 143 of the header tanks 141, 142. In this way, an assembled body of the heat exchanger 100 can be made.

Further, flux (for example, a non-corrosive flux such as fluoro potassium aluminate) is coated on the surface of this assembled body. Then, this assembled body is put into a brazing furnace, the atmosphere in which is an inert gas (for example, nitrogen). In this case, the furnace temperature is approximately 600° C. and the heating time is approximately one hour.

At this time of brazing, as shown in FIG. 6, by the swelling of the core material 110A explained before, the burring portion 112 of the fin 110 is contacted or closely contacted with the wall face 122 of the tube 120 as shown by the arrow in FIG. 6, and the brazing material 110B (shown in FIG. 4), which is clad on the fin 110, gets into a portion between the forward end portion of the burring portion 112 and the wall face 122 and a fillet is formed. In this way, brazing can be conducted. The header tanks 141, 142 and the tube 120 are brazed by the brazing material clad on the header tanks 141, 142. Further, the header tanks 141, 142 and the cap 144, the refrigerant inlet portion 151 and the refrigerant outlet portion 152 are respectively brazed by the brazing material clad on the header tanks 141, 142.

As described above, in the present embodiment, at the temperature (the normal temperature) at which the tube 120 is inserted into each insertion hole 111 of the fin 110, that is, at the temperature (the normal temperature) at which the core portion 101 is assembled, the gap portion 130 is formed between the tube 120 and the burring portion 112. Therefore, the insertion property of the tube 120 can be enhanced. At the time of brazing, the burring portion 112 is positively contacted or closely contacted with the tube 120 side by the swelling of the core material 110A. Therefore, the burring portion 112 can be surely brazed to the tube 120 side. Accordingly, brazing can be positively conducted. As described above, without an increase in the number of man-hours as explained in the item of the prior art, the excellent insertion property and the excellent brazing property of the tube 120 can be ensured.

As the burring portion 112 is formed on the base point of the connecting line 112 a to connect the bottom portions of the cutout portions 114 between the two cutout portions 114, the substantial length of the burring portion 112 can be increased. Therefore, the burring portion 112 can be tightly contacted with the tube 120.

As the direction of the connecting line 112 a, which is the base point of the burring portion 112, is the same as the rolling direction of the fin 110, the direction of the connecting line 112 a is the same as the direction of the metallic crystal grains of the fin 110 determined by rolling. Therefore, the rigidity of the burring portion 112 in the direction of displacement can be lowered. Accordingly, the burring portion 112 can be more smoothly displaced.

As the positioning portions 113 are provided on the end portion sides of the insertion hole 111 in the longitudinal direction, the distance (the gap portion 130) from each burring portion 112 to the opposed tube 120 can be made uniform. Therefore, each burring portion 112 and the tube 120 can be positively contacted or closely contacted with the tube 120.

In this connection, Variation 1 described below may be adopted. As shown in FIG. 7, on the surface of the fin 110 which is a side opposite to the side on which the brazing material 110B is provided, the sacrificial corrosion material 110C (for example, the material of aluminum to which zinc is added) is provided which conducts a sacrificial corrosion action with respect to the tube 120. Due to the foregoing, corrosion on the tube 120 side can be suppressed. Therefore, the life of the heat exchanger can be prolonged by preventing the fluid from leaking out from the tube 120.

Variation 2 described below may be adopted. As shown in FIG. 8, as the brazing material of the fin 110, the brazing material 110B, which corresponds to the first brazing material of the present invention, and the brazing material 110D, which corresponds to the second brazing material of the present invention, are clad on the surface and the reverse face of the core material 110A. In this case, it is set so that the swelling of the core material 110A by the brazing material 110B can be larger than the swelling of the core material 110A by the brazing material 110D. Due to the foregoing, to the portion in which the burring portion 112 and the tube 120 are joined to each other at the time of brazing, the brazing material (the brazing material 110D) can be supplied from a portion located closer to the joining portion. Therefore, the brazing property can be further enhanced.

Next, the second embodiment of the present invention is shown in FIG. 9. The second embodiment is composed in such a manner that the rib 115 is added to the fin 110 of the first embodiment. A cross section of each rib 115 is triangular, and the rib 115 is provided along the side of the fin 110 in the direction in which the tubes 120 are arranged. In this connection, this rib 115 is formed simultaneously when the fin 110 is formed by means of press forming.

Due to the above structure, even when the entire fin 110 is composed of the core material 110A and the brazing material 110B as in the first embodiment described above, at the time of brazing, the displacement of the general portion (the portion of the fin 110 located between the tubes 120) except for the burring portion 112 can be positively suppressed. Alternatively, the displacement of the entire fin 110 can be positively suppressed.

Next, the third embodiment of the present invention is shown in FIGS. 10A, 10B. The third embodiment is composed in such a manner that a portion of the burring portion 112, the rising height of which is high with respect to the opposing side, is provided in the first embodiment described before. The burring portion 112 is composed of a thickness portion between the connecting lines 112 a (the two-dotted chain lines in FIG. 10A) which are opposed to each other in a flat plate state of the fin 110 (a state of development by press forming). In this case, when this thickness portion is obliquely divided so that the burring portions 112, the heights of which are different from each other, can be formed.

Due to the foregoing, in the portion in which the rising height of the burring portion 112 is high, it is possible to obtain a large displacement of the burring portion 112. Therefore, the burring portion 112 can be positively contacted or closely contacted with the tube 120. Therefore, when at least the portion is used as a starting point, the brazing material 110B can get into the gap portion 130 by the capillary phenomenon. Therefore, brazing can be positively conducted.

Next, the fourth embodiment of the present invention is shown in FIG. 11. The fourth embodiment is composed in such a manner that the thickness removing portions 116 from which the thickness is removed into circular holes, are provided in the neighborhood of the connecting line 112 a, which is the base point of the burring portion 112, in the Embodiment 1 described before, Due to the foregoing, the rigidity of the burring portion 112 at the base point can be reduced. Therefore, even when the positional relation is established so that the burring portion 112 can be contacted with the tube 120 at the time of inserting the tube 120, the burring portion 112 can be easily deformed. Accordingly, resistance can be reduced at the time of inserting the tube 120.

Finally, another embodiment will be explained as follows. In the first to the fourth embodiment described above, the displacement action in the burring portion 112 is obtained by the swelling of the core material 110A caused by the brazing material 110B. Instead of that, as shown in FIG. 12, the mother metal layer is composed of two layers. That is, the mother metal layer is composed of aluminum alloy layers, the coefficients of thermal expansion of which are different from each other. That is, the first material member 110A1, which corresponds to the metallic layer of the present invention, and the second material member 110A2, which corresponds to the metallic layer of the present invention, may be laminated. In this structure, the first member 110A1, the coefficient of thermal expansion of which is high, is arranged on the side of the burring portion 112 opposed to the insertion hole side, and the second member 110A2, the coefficient of thermal expansion of which is low, is arranged on the side of the burring portion 112 on the insertion hole 111 side, that is, the second member 110A2, the coefficient of thermal expansion of which is low, is arranged on the side facing the tube 120. In this connection, on the surface of the first member 110A1, the brazing material is clad.

Due to the difference between the coefficients of thermal expansion of the members 110A1, 110A2, the burring portion 112 is warped by the bimetal effect caused by a rise in the temperature at the time of brazing, and the burring portion 112 positively comes into contact with the tube 120. Further, the penetration of the brazing material is added and the burring portion 112 is further warped and positively contacted with the tube 120. In this connection, a material, the penetration of which is small, may be used for the brazing material and the burring portion 112 may be contacted with the tube 110 only by the bimetal effect of the aluminum alloy layer.

In the first to the fourth embodiment described above, the burring portions 112 are provided on both sides of the tube 120, however, the burring portion 112 may be provided only on one side of the tube 120. For example, the burring portion 112, capable of being deformed by a change in the temperature, can be provided being opposed only to a main face of the flat tube 120. In the fin 110, a cutting end face can be arranged being opposed to the other main face of the flat tube 120. Alternatively, in the fin 110, a receiving face, which is deformed only a little with respect to a temperature change, can be formed. Alternatively, in the fin 110, a receiving face, which is not deformed at all with respect to a temperature change, can be formed.

Concerning the shape of the burring portion 112, with respect to the shape of the burring portion 112 of the first embodiment described before, as shown in FIGS. 13A to 14B, the rising point 117 is formed between the connecting line 112 b (the base point) and the forward end portion, and the burring portion 112 may be formed obliquely or vertically toward the forward end portion of this rising point 117.

The gap portion 130 may be substantially zero at the time of inserting the tube 120, that is, the burring portion 112 is contacted with the tube 120 at the time of inserting the tube 120, and the burring portion 112 may be positively, closely contacted with the tube 110 by the displacement action at the time of brazing.

Alternatively, the tube 120 is inserted at a predetermined temperature (for example, at a low temperature), so that the gap portion 130 can be ensured. At the initial stage of the displacement action conducted at the normal temperature, the burring portion 112 may be contacted with the tube 110, and further the burring portion 112 may be closely contacted with the tube 110 at the time of brazing.

In this connection, in the case where the tube 120 is contacted with the burring portion 112 at the time of insertion or alternatively in the case where a positional dislocation of the tube 120 with respect to the insertion hole 111 is small, the positioning portion 113 may be omitted.

In the case where a sufficiently large displacement action can be obtained by selecting an appropriate material, the cutout portion 114 may be omitted.

The above explanations are made into the case in which aluminum material is mainly used. However, it should be noted that the present invention is not limited to the above specific embodiment. Copper material or stainless steel may be applied to the present invention. Further, the objective heat exchanger is not limited to the air heat exchanger 100 used for a heat pump. As long as the fin 110 composing the core portion 101 is of the plate-type and as long as the tube 120 is brazed after it has been inserted, the present invention can be applied to various components such as a radiator, a heater core and a condenser.

While the invention has been described by reference to specific embodiments chosen for purposes of illustration, it should be apparent that numerous modifications could be made thereto, by those skilled in the art, without departing from the basic concept and scope of the invention. 

1. A heat exchanger comprising: a plurality of plate-shaped fins, which are laminated at predetermined intervals, on which a plurality of insertion holes having burring portions are formed; and a plurality of tubes inserted into the insertion holes, wherein the burring portions and the tubes are brazed to each other, and at least the burring portions of the plate-shaped fins are composed of a plurality of metallic layers for displacing the burring portions to the side of the insertion holes according to a rise in the temperature at the time of brazing.
 2. A heat exchanger according to claim 1, wherein the metallic layer is composed of a core material and a brazing material clad onto one of the faces of the core material.
 3. A heat exchanger according to claim 2, wherein a sacrificial material, which conducts a sacrificial corrosion action upon the tube is provided on a face of the metallic layer opposite to the face on which the brazing material is provided.
 4. A heat exchanger according to claim 1, the metallic layer including: a core material; a first brazing material; and a second clad material, wherein and the first brazing material and the second clad material are respectively clad on a surface and a reverse face of the core material.
 5. A heat exchanger according to claim 1, wherein the direction in which rising points of the burring portions are connected to each other is the same as a rolling direction of the plate-shapes fins.
 6. A heat exchanger according to claim 1, wherein a cross section of the tube is formed into a flat shape, the burring portions are formed on two sides of the insertion hole corresponding to a long side of the flat cross section of the tube, and a positioning portion for positioning the tube is provided in a portion of the insertion hole corresponding to an end portion of the flat cross section in the longitudinal direction.
 7. A heat exchanger according to claim 1, wherein two cutout portions, which are cut out onto the side opposite to the insertion hole side, are formed at a peripheral edge of the insertion hole, and the burring portion is formed at a base point of a connecting line to connect bottom portions of the cutout portions between the two cutout portions.
 8. A heat exchanger according to claim 1, wherein a rib, which is extended along a side portion of the plate-shaped fin, is provided in the side portion of the plate-shaped fin in a direction in which a plurality of tubes are arranged.
 9. A heat exchanger according to claim 1, wherein the burring portions are arranged at the peripheral edge of the insertion hole being opposed to each other, and a portion, the rising height of which is higher than the opposing side, is formed in each burring portion.
 10. A heat exchanger according to claim 7, wherein a thickness removing portion is formed in the neighborhood of a portion where the rising points of the burring portions are connected to each other or in the neighborhood of the base point.
 11. A heat exchanger according to claim 1, the burring portion including: a first metallic layer arranged on the insertion hole side; and a second metallic layer, which is arranged on the side opposite to the insertion hole side, to be penetrated into the first metallic layer and to swell the first metallic layer so that the burring portion can be displaced to the insertion hole side.
 12. A heat exchanger according to claim 1, the burring portion including a plurality of metallic layers, the coefficients of thermal expansion of which are different from each other so as to exhibit the bimetal effect so that the burring portion can be displaced to the insertion hole side.
 13. A method of manufacturing a heat exchanger comprising the steps of: laminating a plurality of plate-shaped fins, in which a plurality of insertion holes having the burring portions are formed, at regular intervals; inserting a plurality of tubes into the insertion holes; and brazing the burring portions and the tubes to each other, wherein at least the burring portions of the plate-shaped fins are composed of a plurality of metallic material layers so that the burring portions can be displaced to the insertion holes side according to a rise in the temperature to the brazing temperature, and after the tubes have been inserted into the insertion holes, the burring portions are displaced and contacted with the tubes and brazing is conducted.
 14. A method of manufacturing a heat exchanger according to claim 13, wherein gaps are formed between the burring portions and the tubes when the tubes are inserted into the insertion holes.
 15. A method of manufacturing a heat exchanger according to claim 14, wherein the tubes are inserted into the insertion holes at the normal temperature.
 16. A method of manufacturing a heat exchanger according to claim 13, the burring portion including: a first metallic layer arranged on the insertion hole side; and a second metallic layer, which is arranged on the side opposite to the insertion hole side, to be penetrated into the first metallic layer and to swell the first metallic layer so that the burring portion can be displaced to the insertion hole side.
 17. A method of manufacturing a heat exchanger according to claim 13, the burring portion including: a plurality of metallic layers, the coefficients of thermal expansion of which are different from each other so as to exhibit the bimetal effect so that the burring portion can be displaced to the insertion hole side.
 18. A plate-shaped fin used for a heat exchanger in which the burring portions are provided in the insertion holes into which a plurality of tubes are inserted, wherein at least the burring portions are composed of a plurality of metallic material layers, and the burring portions are displaced to the insertion hole side according to a rise in the temperature to the temperature at the time of brazing.
 19. A plate-shaped fin used for a heat exchanger according to claim 18, wherein the metallic layer is composed of a core material and a brazing material clad on one of the faces of the core material.
 20. A plate-shaped fin used for a heat exchanger according to claim 19, wherein a sacrificial corrosion layer, which conducts a sacrificial corrosion action upon the tube, is provided on a face opposite to the face on which the brazing material is provided.
 21. A plate-shaped fin used for a heat exchanger according to claim 18, the metallic layer including: a core material; a first brazing material; and a second clad material, wherein and the first brazing material and the second clad material are respectively clad on a surface and a reverse face of the core material.
 22. A plate-shaped fin used for a heat exchanger according to claim 18, wherein a direction in which rising points of the burring portions are connected to each other is the same as its rolling direction.
 23. A plate-shaped fin used for a heat exchanger according to claim 18, wherein a cross section of the tube is formed into a flat shape, the burring portions are formed on two sides of the insertion hole corresponding to a long side of the flat cross section of the tube, and a positioning portion for positioning the tube is provided in a portion of the insertion hole corresponding to an end portion of the flat cross section in the longitudinal direction.
 24. A plate-shaped fin used for a heat exchanger according to claim 18, wherein two cutout portions, which are cut out onto the side opposite to the insertion hole side, are formed at a peripheral edge of the insertion hole, and the burring portion is formed at a base point of a connecting line to connect bottom portions of the cutout portions between the two cutout portions.
 25. A plate-shaped fin used for a heat exchanger according to claim 18, wherein a rib, which is extended along a side portion of the plate-shaped fin, is provided in the side portion of the plate-shaped fin in a direction in which the tubes are arranged.
 26. A plate-shaped fin used for a heat exchanger according to claim 18, wherein the burring portions are arranged at the peripheral edge of the insertion hole being opposed to each other, and a portion, the rising height of which is higher than the opposing side, is formed in each burring portion.
 27. A plate-shaped fin used for a heat exchanger according to claim 20, wherein a thickness removing portion is formed in the neighborhood of a portion where the rising points of the burring portions are connected to each other or in the neighborhood of the base point.
 28. A plate-shaped fin used for a heat exchanger according to claim 18, the burring portion including: a first metallic layer arranged on the insertion hole side; and a second metallic layer, which is arranged on the side opposite to the insertion hole side, to be penetrated into the first metallic layer and to swell the first metallic layer so that the burring portion can be displaced to the insertion hole side.
 29. A plate-shaped fin used for a heat exchanger according to claim 18, the burring portion including: a plurality of metallic layers, the coefficients of thermal expansion of which are different from each other so as to exhibit the bimetal effect so that the burring portion can be displaced to the insertion hole side. 